WO2019049917A1

WO2019049917A1 - Flux

Info

Publication number: WO2019049917A1
Application number: PCT/JP2018/032958
Authority: WO
Inventors: 知久川中子; 美幸平岡; 貴洋西▲崎▼; 直克児島; 浩由川▲崎▼
Original assignee: 千住金属工業株式会社
Priority date: 2017-09-06
Filing date: 2018-09-06
Publication date: 2019-03-14
Also published as: JP6688267B2; US20210060713A1; TW201917113A; KR20200051649A; CN111107961A; JP2019042788A

Abstract

Provided is a flux which enables improvement of solderability, while maintaining activeness by suppressing the formation of an ester by a reaction between an organic acid and a hydroxy group of an alcohol that is contained in a solvent. A flux which contains from 40 mass% to 90 mass% (inclusive) of water, from 2 mass% to 15 mass% (inclusive) of an organic acid, and more than 0 mass% but 48 mass% or less of a solvent that has a hydroxy group, and which is configured such that the content ratio of carboxylic acid ester units that are esterified by the organic acid and the hydroxy group contained in the solvent is from 0 unit mol% to 50 unit mol% (inclusive) if the molar mass% of organic acid carboxyl group units in the organic acid is taken as 100 unit mol%.

Description

flux

The present invention relates to a water-containing flux.

There are various methods for forming solder bumps on a substrate. With the recent miniaturization of solder balls, a method of transferring flux to the solder balls and mounting the fluxed solder balls on the electrodes has come to be adopted. By reflowing and cooling the substrate on which the solder balls are mounted, solder bumps are formed.

The flux chemically removes the metal oxide film present on the metal surface of the solder alloy and the object to be joined which is to be soldered, and enables the movement of the metal element at the boundary between the two. For this reason, by soldering using a flux, an intermetallic compound is formed between the solder alloy and the metal surface of the bonding object, and a strong bonding can be obtained. There are fluxes containing an organic acid, a solvent and the like. The organic acid is added as an activator component for removing the metal oxide film, and the solvent has a role of dissolving solid components in the flux. There is also a flux containing water, for example, Patent Document 1 discloses a flux containing 0.1 to 0.4% by weight of water based on the total amount.

JP 2005-74449 A

Among the fluxes, there are some flux residues that remain on the premise of cleaning after soldering. The flux residue leads to deterioration of solderability such as solder joint failure, conduction failure and the like. Therefore, in order to construct the composition of the flux which does not require cleaning or the composition of the water-cleanable flux, an attempt is made to reduce the flux residue. A low residue flux can be designed by replacing a part or all of the base agent which has low reactivity with organic acids and is difficult to volatilize during reflow with a highly volatile solvent or the like. However, the organic acid gradually reacts with the hydroxyl group (—OH group) of the alcohol in the solvent, which is contained in a larger amount than the conventional one, and becomes easy to esterify with the passage of time from the preparation of the flux to the use.

When the organic acid forms an ester, the activity of removing the metal oxide film possessed by the organic acid is inactivated. If the removal of the metal oxide film is insufficient, there is a problem that the solder alloy and the object to be joined can not be firmly joined. The flux disclosed in Patent Document 1 mentioned above has not taken into consideration such a problem at all.

Therefore, the present invention solves such problems, and suppresses the formation of an ester by the reaction of the organic acid and the hydroxyl group of the alcohol contained in the solvent, and maintains the activity, as well as the solder The purpose is to provide a flux that improves the stickability.

The technical means of the present invention adopted to solve the above-mentioned problems are as follows.
(1) Organic acid carboxyl, which contains 40% by mass or more and 90% by mass or less of water, 2% by mass or more and 15% by mass or less of an organic acid, and 0% by mass to 48% by mass or less of a solvent having a hydroxy group The content ratio of the carboxylic acid ester unit esterified by the hydroxy group and the organic acid contained in the solvent is 0 unit mol% or more and 50 unit mol% or less, when the molar mass% of the group unit is 100 unit mol%. Organic acid, glutaric acid, phenyl succinic acid, succinic acid, malonic acid, adipic acid, azelaic acid, glycolic acid, diglycolic acid, thioglycolic acid, thiodiglycolic acid, propionic acid, 2,2-bishydroxymethyl acid At least one of propionic acid, 2,2-bishydroxymethylbutanoic acid, malic acid, tartaric acid and trimer acid Flux, characterized in that it contains.

In the present invention, the "organic acid carboxyl group unit" indicates a functional group of a carboxyl group having activity as an organic acid, and the "carboxylic acid ester unit" indicates a functional group in a state where the carboxyl group is esterified. And "unit mol%" means mol mass% of each "unit".

(2) The flux described in the above (1), wherein the content ratio of water is 40% by mass to 80% by mass.

(3) The flux described in the above (1) or (2), wherein the content ratio of the solvent is 8% by mass to 48% by mass.

(4) The amine contains more than 0% by mass and 10% or less by mass, and the amine is imidazoles, aliphatic amines, aromatic amines, amino alcohols, polyoxyalkylene type alkylamines, terminal amine polyoxyalkylenes, amine hydrogen halides The flux according to any one of the above (1) to (3), which contains at least one of acid salts.

In the flux of the present invention, since the hydrolysis occurs due to the water content, it is possible to suppress the reaction between the organic acid and the hydroxy group contained in the solvent to form an ester. Therefore, the metal oxide film can be sufficiently removed. Also, the solderability is good.

Hereinafter, the flux as an embodiment concerning the present invention is explained. The flux of the present embodiment contains 40% by mass to 90% by mass of water, 2% by mass to 15% by mass of an organic acid, and 0% by mass to 48% by mass of a solvent having a hydroxy group. Pure water can be used as water, and the content ratio of water is more preferably 40% by mass to 80% by mass. The content ratio of the solvent is more preferably 8% by mass to 48% by mass.

The organic acid is preferably a water-soluble organic acid, and is added as an activator component in the flux. By this activator component, at the time of soldering, the solder alloy and the metal oxide present on the metal surface of the object to be soldered are chemically removed. Examples of organic acids include glutaric acid, phenylsuccinic acid, succinic acid, malonic acid, adipic acid, azelaic acid, glycolic acid, diglycolic acid, thioglycolic acid, thiodiglycolic acid, propionic acid, 2,2-bishydroxymethyl At least one of propionic acid, 2,2-bishydroxymethylbutanoic acid, malic acid, tartaric acid, dimer acid, hydrogenated dimer acid, trimer acid and the like is used. These organic acids have a carboxyl group. As an example of the organic acid, a monofunctional organic acid has one carboxyl group and is represented by the following chemical formula.

However, R1 in the formula is a linear or branched alkyl group, an alkyl ether group or the like. Also, R1 may contain an aromatic ring. The bifunctional organic acid has two carboxyl groups, and the trifunctional or higher organic acid has three or more carboxyl groups. As the functional group molar number of the carboxyl group having activity as an organic acid (hereinafter referred to as "organic acid carboxyl group unit") increases in the flux, the activity acting on the removal of the metal oxide film is stronger. For example, a monofunctional organic acid has 1 mol of an organic acid carboxyl group unit, a bifunctional organic acid has 2 mol of an organic acid carboxyl group unit, and a trifunctional organic acid has 1 mol of organic acid per 1 mol of organic acid. The organic acid carboxyl group unit is 3 moles.

As the solvent, one having a hydroxy group is used. The solvent preferably has water solubility, and preferably does not volatilize in a low temperature range of 120 ° C. to 150 ° C. in order to efficiently bring about the action of the active agent. If the solvent is volatilized, the flux becomes dry, and it becomes difficult for the flux to wet and spread at the joint. Therefore, the boiling point of the solvent is preferably 200 ° C. or more. Further, it is preferable to use a solvent that volatilizes at the reflow temperature, and the boiling point of the solvent is preferably 280 ° C. or less. As the solvent, 1,3-propanediol, hexylene glycol, hexyl diglycol, 1,3-butanediol, 2-ethyl-1,3-hexanediol, 2-ethylhexyl diglycol, phenyl glycol, butyl triglycol, Preferably, at least one of terpineol and the like is used. These solvents are represented by the following chemical formula.

However, R 2 in the formula is a linear or branched alkyl group, an alkyl ether group or the like, and R 2 may contain an aromatic ring.

For the flux of the present embodiment, for example, imidazoles, aliphatic amines, aromatic amines, amino alcohols, polyoxyalkylene type alkylamines, terminal amine polyoxyalkylenes, amine hydrohalide salts, etc. described below. It may contain at least one of amines. An amine is added as an active auxiliary component in the flux. Amines react with organic acids to form salts and increase heat resistance. When a large amount of amine is added, the amount of flux residue increases. Therefore, it is preferable that the content be 0% by mass or more and 10% by mass or less. The amine in the present embodiment is preferably an amine having a molecular weight of 700 or less, more preferably 600 or less.

The imidazoles include imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-benzyl-2-phenylimidazole and the like. Aliphatic amines include methylamine, ethylamine, dimethylamine, 1-aminopropane, isopropylamine, trimethylamine, n-ethylmethylamine, allylamine, n-butylamine, diethylamine, sec-butylamine, tert-butylamine, N, N- Dimethylethylamine, isobutylamine, pyrrolidine, 3-pyrroline, n-pentylamine, dimethylaminopropane, 1-aminohexane, triethylamine, diisopropylamine, dipropylamine, hexamethyleneimine, 1-methylpiperidine, 2-methylpiperidine, 4 -Methylpiperidine, cyclohexylamine, diallylamine, n-octylamine, aminomethyl, cyclohexane, n-octylamine, 2-ethylhexylamine, dibutylamine Emissions, diisobutyl amine, 1,1,3,3-tetramethylbutyl amine, 1-cyclohexylethyl amine, N, N-dimethylcyclohexylamine, and the like. Aromatic amines include aniline, diethylaniline, pyridine, diphenyl guanidine, ditolyl guanidine and the like. Examples of amino alcohols include 2-ethylaminoethanol, diethanolamine, diisopropanolamine, N-butyldiethanolamine, triisopropanolamine, N, N-bis (2-hydroxyethyl) -N-cyclohexylamine, triethanolamine, N, N And N, N ', N'-tetrakis (2-hydroxypropyl) ethylenediamine, N, N, N', N '', N ''-pentakis (2-hydroxypropyl) diethylene triamine and the like. Examples of polyoxyalkylene type alkylamines include polyoxyalkylene alkylamines, polyoxyalkylene ethylenediamines, and polyoxyalkylene diethylenetriamines. The terminal amine polyoxyalkylene includes terminal amino polyethylene glycol-polypropylene glycol copolymer (terminal amino PEG-PPG copolymer) and the like. As the amine hydrohalide salt, for the hydrohalide salts (hydrofluoride, borohydrofluoride, hydrochloride, hydrobromide, hydroiodide) of the various amines mentioned above And ethylamine hydrochloride, ethylamine hydrobromide, cyclohexylamine hydrochloride, cyclohexylamine hydrobromide and the like.

For the flux of the present embodiment, for example, trans-2,3-dibromo-2-butene-1,4-diol, 2,3-dibromo-1,4-butanediol, 2,3-dibromo-1 Of at least one halogen compound of propanol, 2,3-dichloro-1-propanol, 2,2,2-tribromoethanol, 1,1,2,2-tetrabromoethane etc. You may contain in the range which does not impair.

For the flux of the present embodiment, for example, polyoxyethylene ethylene diamine, polyoxypropylene ethylene diamine, polyoxyethylene polyoxypropylene ethylene diamine, polyoxyethylene alkylamine, polyoxyethylene tallow amine, polyoxyethylene alkylpropyl diamine, poly At least one surfactant of oxyethylene tallow propyl diamine, polyoxyethylene alkyl ether, polyoxyethylene alkyl amide, aliphatic alcohol ethylene oxide adduct, etc. may be contained within the range not to impair the performance of the present flux. . Surfactants adjust the surface tension of the flux. The surfactant of the present embodiment preferably has a molecular weight of more than 700.

Furthermore, colorants such as dyes, pigments and dyes, antifoaming agents, thixotropic agents and the like may be appropriately added to the flux of the present embodiment as long as the performance of the flux is not impaired.

When the organic acid reacts with the hydroxy group contained in the solvent, the organic acid forms an esterified organic acid ester to produce water. A monofunctional organic acid is used as an example of an organic acid, and a monofunctional alcohol is used as an example of a solvent. The reaction of an organic acid and a hydroxy group in the solvent is shown by the following reaction formula (1) Be The reaction of a bifunctional or trifunctional or higher organic acid or alcohol also occurs with a hydroxyl group for each carboxyl group, and thus the description thereof is omitted.

The organic acid ester (R1COOR2) does not have the activity of removing the metal oxide film as a flux that the organic acid had. Therefore, the flux containing the organic acid and the solvent having a hydroxy group may lose the activity as a flux for removing the metal oxide film.

The esterification reaction of the reaction formula (1) is a reversible equilibrium reaction, and in the environment where the organic acid ester and water coexist, the hydrolysis shown in the following reaction formula (2) also occurs.

That is, when an organic acid and a solvent having a hydroxy group are mixed in a flux, both reactions of reaction formulas (1) and (2) take place, and after a predetermined time has elapsed, the respective reaction rates become equilibrium. become.

Here, the number of moles of the functional group unit due to the esterification of the organic acid when the reactions of the reaction formulas (1) and (2) are in equilibrium will be described. The activity of the organic acid is higher as the number of moles of the organic acid carboxyl group is larger, and the activity of the organic acid is weaker as the number of moles of the organic acid carboxyl group is smaller.

First, the reaction of monofunctional organic acid being esterified is shown in reaction formula (3). When the organic acid and the hydroxy group react, as described in the reaction formula (1), a dehydration reaction occurs to form an organic acid ester. Hereinafter, the functional group in the state in which the carboxyl group is esterified is referred to as a "carboxylic acid ester unit", and the molar mass% of the functional group is referred to as a "unit molar%".

Assuming that the reaction of reaction formulas (1) and (2) is in equilibrium and the number of moles of organic acid and organic acid ester in the flux is the same, the total of organic acid and organic acid ester is 100 mol%. 50 mol% of the organic acid and 50 mol% of the organic acid ester. Since one carboxyl group possessed by one organic acid and one ester group possessed by one organic acid ester are also present, the organic acid carboxyl group unit of the organic acid added to the flux is 100 unit mol%, The acid carboxyl group unit is 50 unit mol%, and the carboxylic acid ester unit is 50 unit mol%. That is, the unit mole percent of the carboxyl group and the unit mole percent of the ester group have the same value.

Next, a reaction for esterifying a bifunctional organic acid is shown in reaction formula (4).

When the bifunctional organic acid shown in the leftmost of reaction formula (4) is esterified, first, an organic acid monoester shown in the center of reaction formula (4) in which one carboxyl group out of two carboxyl groups is esterified Is formed. When the esterification proceeds further, the organic acid diester shown in the rightmost of the reaction formula (4) is formed in which two carboxyl groups are esterified.

When an equilibrium state is reached and an organic acid monoester is formed, when the total number of organic acid and organic acid monoester is 100 mol%, when the number of moles of organic acid and organic acid monoester in the flux is the same, The acid is 50 mole% and the organic acid monoester is 50 mole%. Since there are two carboxyl groups possessed by one organic acid, one carboxyl group possessed by one organic acid monoester, and one ester group, the ratio of the organic acid carboxyl group unit to the carboxylic acid ester unit is 3: It is 1. Therefore, when the organic acid carboxyl group unit of the organic acid added to the flux is 100 unit mol%, the organic acid carboxyl group unit is 75 unit mol% and the carboxylic acid ester unit is 25 unit mol%.

When an equilibrium state is reached and an organic acid diester is formed, the carboxyl group possessed by the organic acid and the ester group possessed by the organic acid diester are also two, so when the same number of organic acid and organic acid diester exist, the organic acid carboxyl is The abundance ratio of the base unit to the carboxylic acid ester unit is 1: 1. When the organic acid carboxyl group unit of the organic acid added to the flux is 100 unit mol%, 50 unit mol% of the carboxyl group unit and 50 unit mol% of the carboxylic acid ester unit are obtained.

When the content ratio of the carboxylic acid ester unit is 0 unit mol% to 50 unit mol% when the organic acid carboxyl group unit of the organic acid added to the flux is 100 unit mol%, the organic acid carboxyl group unit Is present in the range of 50 mol% to 100 mol%, the activity of the organic acid is sufficiently present.

Next, the relationship between the concentrations of the organic acid and the organic acid ester when the reactions of the reaction formulas (1) and (2) are in equilibrium will be described. When the type of organic acid and solvent, and the flux temperature are fixed, the ester concentration in the flux is determined by the following equilibrium constant equation (5).

However, K1: equilibrium constant [R1COOR2]: concentration of organic acid ester [H ₂ O]: concentration of water [R 1 COOH]: concentration of organic acid [R 2 OH]: concentration of alcohol There is no change in the Therefore, the equilibrium constant equation (5) can be approximated to the equilibrium constant equation (6).

However, K2: equilibrium constant

Referring to the equilibrium constant equation (6), the reaction constant of equation (2) is promoted by raising the concentration of water [H ₂ O] to keep the equilibrium constant constant, and the organic acid not esterified is It is believed that the concentration [R1 COOH] can be increased. On the other hand, when the flux contains a large amount of water, when the heated water bumps during the reflow, a state in which the solder is detached from the electrode (ball missing) occurs. Ball missing causes solder joint failure and conduction failure. Therefore, in order to determine the proportion of the composition contained in the flux which improves the solderability while suppressing the formation of the ester, the flux shown in Table 1 and Table 2 shows the flux of each Example and each Comparative Example. Were prepared, and each flux was subjected to esterification suppression verification and ball-missing suppression verification as follows.

Hereinafter, although the specific example of the flux which concerns on this invention is shown in an Example, this invention is not limited to the following specific examples. Moreover, the numerical value without a unit shows mass% in the following tables.

(I) About esterification suppression verification (A) Evaluation method The acid value of each flux of each example and comparative example was measured according to JIS K 0070 using potassium hydroxide. After storing the flux at 40 ° C. for 4 weeks, the acid value of each flux was measured. The reduction rate of the acid value of each flux was calculated.

(B) Judgment criteria ○: The decrease rate of the acid value was within 50%. ×: The decrease rate of the acid value exceeded 50%.

The acid value refers to the number of milligrams of potassium hydroxide necessary to neutralize the acid contained in 1 g of flux. The higher the acid number of the flux, the larger the number of moles of organic acid carboxyl group units in the flux, and the lower the acid number of the flux, the smaller the number of moles of organic acid carboxyl group units in the flux.

That is, when the organic acid reacts with the hydroxy group contained in the solvent to form an organic acid ester, the number of moles of the organic acid carboxyl group unit in the flux decreases, and the acid value decreases. Therefore, it can be said that the flux with a higher rate of decrease in acid value after 4 weeks has a higher percentage of esterified organic acid, but the lower the rate of decrease in acid number, the more esterification of the organic acid was suppressed It can be said that it is flux.

When the organic acid is esterified, the activity of removing the metal oxide film is lost. The flux in which the esterification of the organic acid is suppressed can sufficiently remove the metal oxide film present on the metal surface, so that the solder alloy and the object to be joined can be firmly joined. When the reduction rate of the acid value is 50% or less, the content ratio of esterified carboxylic acid ester unit is 0 unit mol% when the organic acid carboxyl group unit added to the flux is 100 unit mol% Although the content is 50 unit mol% or less, it can be said that the organic acid has the property of removing the metal oxide film sufficiently. Therefore, the inventors found that the flux in which the reduction rate of the acid value became 50% or less was a flux capable of suppressing the esterification of the organic acid.

(II) Ball-Missing Suppression Verification In the ball-Missing suppression verification, the flux of each Example and Comparative Example was verified under the following two conditions: Condition 1 and Condition 2.

(A) Evaluation method: Condition 1
Solder balls having a diameter of 600 μm were prepared with a composition of Sn-3Ag-0.5Cu. Each of the prepared solder balls was coated with the flux of each Example and Comparative Example, and then each solder ball to which the flux was applied was mounted on the electrode of the substrate. Then, the substrate was heated at a temperature of 100 ° C. for 1 minute using a high-speed heater, and then heated at 250 ° C. for 5 seconds. Then, it cooled at room temperature. The appearance of the electrode after cooling to room temperature was visually confirmed.

(B) Evaluation method: Condition 2
Solder balls having a diameter of 600 μm were prepared with a composition of Sn-3Ag-0.5Cu. Each of the prepared solder balls was coated with the flux of each Example and Comparative Example, and then each solder ball to which the flux was applied was mounted on the electrode of the substrate. Then, the substrate was heated at 110 ° C. for 1 minute using a high-speed heater, and then heated at 250 ° C. for 5 seconds. Then, it cooled at room temperature. The appearance of the electrode after cooling to room temperature was visually confirmed.

(C) Judgment criteria ○: In the verification under conditions 1 and 2, the solder remained without coming off the electrode.
○: In the verification according to condition 1, the solder remained without coming off the electrode.
X: In the verification according to the conditions 1 and 2, the solder detached from the electrode and a ball missing occurred.

Ball missing causes solder joint failure and conduction failure. When the solder remains on the electrode after heating, a solder bump can be formed in which bonding failure or conduction failure is suppressed. Incidentally, since the temperature condition is stricter than the condition 1 under the condition 2, it can be judged that the flux in which the ball missing is not found in the verification according to the condition 1 is a flux having a sufficiently good solderability. The flux for which ball missing was not found in the verification according to the conditions 1 and 2 is judged to be a flux with better solderability.

The flux of Example 1 contains 40% by mass of pure water, 15% by mass of malic acid as an organic acid, and 45% by mass of 1,3-propanediol as a solvent. The flux of Example 1 was able to suppress the esterification, and in the conditions 1 and 2, no ball missing occurred.

The flux of Example 2 contains 40% by mass of pure water, 15% by mass of malic acid, 10% by mass of imidazole as an amine, and 35% by mass of 1,3-propanediol. The flux of Example 2 was able to suppress esterification, and in the conditions 1 and 2, no ball missing occurred.

The flux of Example 3 contains 50% by mass of pure water, 2% by mass of malonic acid as an organic acid, and 48% by mass of 1,3-propanediol. The flux of Example 3 was able to suppress the esterification, and in the conditions 1 and 2, no ball missing occurred.

The flux of Example 4 contains 50% by mass of pure water, 2% by mass of malic acid, and 48% by mass of 1,3-propanediol. The flux of Example 4 was able to suppress the esterification, and in the conditions 1 and 2, no ball missing occurred.

The flux of Example 5 contains 60% by mass of pure water, 2% by mass of malonic acid, and 38% by mass of 1,3-propanediol. The flux of Example 5 was able to suppress the esterification, and in the conditions 1 and 2, no ball missing occurred.

The flux of Example 6 contains 70% by mass of pure water, 2% by mass of malonic acid, and 28% by mass of 1,3-propanediol. The flux of Example 6 was able to suppress the esterification, and in the conditions 1 and 2, no ball missing occurred.

The flux of Example 7 contains 80% by mass of pure water, 2% by mass of malonic acid, and 18% by mass of 1,3-propanediol. The flux of Example 7 was able to suppress the esterification, and in the conditions 1 and 2, no ball missing occurred.

The flux of Example 8 contains 90% by mass of pure water, 2% by mass of malonic acid, and 8% by mass of 1,3-propanediol. The flux of Example 8 was able to suppress the esterification, and no ball missing occurred under the condition 1.

The flux of Example 9 contains 40% by mass of pure water, 15% by mass of malic acid, 1% by mass of imidazole, and 44% by mass of 1,3-propanediol. The flux of Example 9 was able to suppress the esterification, and in the conditions 1 and 2, no ball missing occurred.

The flux of Comparative Example 1 does not contain pure water, and contains 2% by mass of malonic acid and 98% by mass of 1,3-propanediol. In the flux of Comparative Example 1, no ball missing occurred under the conditions 1 and 2, but the decrease in acid value exceeded 50%, so the suppression of esterification was insufficient.

The flux of Comparative Example 2 does not contain pure water, and contains 5% by mass of malic acid, 1% by mass of imidazole, and 94% by mass of 1,3-propanediol. In the flux of Comparative Example 2, no ball misting occurred under the conditions 1 and 2, but the reduction in acid value exceeded 50%, so that the suppression of esterification was insufficient.

The flux of Comparative Example 3 contains 0.1% by mass of pure water, 2% by mass of malonic acid, and 97.9% by mass of 1,3-propanediol. In the flux of Comparative Example 3, no ball misting occurred under the conditions 1 and 2, but the decrease in acid value exceeded 50%, so that the suppression of esterification was insufficient.

The flux of Comparative Example 4 contains 5% by mass of pure water, 2% by mass of malonic acid, and 93% by mass of 1,3-propanediol. Although no ball missing occurred under conditions 1 and 2, the reduction of the acid value exceeded 50%, so that the suppression of esterification was insufficient.

The flux of Comparative Example 5 contains 10% by mass of pure water, 2% by mass of malonic acid, and 88% by mass of 1,3-propanediol. In the flux of Comparative Example 5, no ball misting occurred under the conditions 1 and 2, but the decrease in acid value exceeded 50%, so the suppression of esterification was insufficient.

The flux of Comparative Example 6 contains 10% by mass of pure water, 2% by mass of malic acid, and 88% by mass of 1,3-propanediol. In the flux of Comparative Example 6, no ball misting occurred under the conditions 1 and 2, but the decrease in acid value exceeded 50%, so the suppression of esterification was insufficient.

The flux of Comparative Example 7 contains 20% by mass of pure water, 2% by mass of malonic acid, and 78% by mass of 1,3-propanediol. In the flux of Comparative Example 7, no ball missing occurred under the conditions 1 and 2, but the decrease in acid value exceeded 50%, so that the suppression of esterification was insufficient.

The flux of Comparative Example 8 contains 30% by mass of pure water, 2% by mass of malonic acid, and 68% by mass of 1,3-propanediol. In the flux of Comparative Example 8, no ball missing occurred under the conditions 1 and 2, but the reduction in acid value exceeded 50%, so that the suppression of esterification was insufficient.

The flux of Comparative Example 9 contains 98% by mass of pure water and 2% by mass of malonic acid. In the flux of Comparative Example 9, ball missing occurred under conditions 1 and 2. Since the flux of Comparative Example 9 did not contain a solvent, the organic acid was not esterified.

The flux in Example 7, Example 8, and Comparative Example 9 contained the same components, but in Example 7, no ball missing occurred under conditions 1 and 2 in Example 7, and no ball occurred in Condition 1 in Example 8 Without the ball, in Comparative Example 9, ball missing occurred under conditions 1 and 2. It can be said that this is because the proportions of water contained in the fluxes of Examples 7 and 8 and Comparative Example 9 are different from each other, and if the proportion of water is large, it can be said to cause ball missing. From these results, the content ratio of water is preferably 90% by mass or less, and more preferably 80% by mass or less.

In the flux of Example 1 in which the content ratio of water is 40% by mass, esterification could be suppressed, but in the flux of Comparative Example 8 in which the content ratio of water is 30% by mass, the decrease in acid value exceeds 50%, Of esterification could not be sufficiently suppressed. From the results of Example 1 and Comparative Example 8, it can be said that suppression of esterification is insufficient when the content ratio of water is small, but the content ratio of water is preferably 40% by mass or more, and the content ratio of water is It can be said that esterification of the organic acid is suppressed as the amount is larger.

The fluxes of Examples 1 to 9 all contain water in an amount of 40% by mass to 90% by mass. In any of the examples, esterification could be suppressed, and no ball missing occurred under condition 1. Therefore, it can be said that the content ratio of water is preferably 40% by mass or more and 90% by mass or less. Furthermore, in the flux of Examples 1 to 7 and 9 in which the content ratio of water is 40% by mass to 80% by mass, no ball missing occurs even under the condition 2. From this, it can be said that the content ratio of water is more preferably 40% by mass to 80% by mass. In addition, although each verification was performed using a pure water in this example, the same result was obtained, even if it used various pure waters, such as distilled water and ion exchange water.

In the conventional flux, the water in the flux is contained so as to be as small as possible. The reason is that, as described above, when the flux contains a large amount of water, when the water is heated and bumped, the solder is detached from the electrode and leads to ball-mising, causing a solder joint failure or a conductive failure. In the flux of this example, even if it contained 40% by mass or more and 90% by mass, which is more water than the conventional flux, it was possible to suppress the ball missing. This is considered to be because water in the flux was used for decomposition of the organic acid ester as shown in reaction formula (2).

The fluxes of Examples 1 to 9 contained 2% by mass to 15% by mass of the organic acid, and in any of the examples, esterification was suppressed, and no ball missing occurred under the condition 1. From this, it can be said that the content rate of the organic acid is preferably 2% by mass or more and 15% by mass or less.

Although different organic acids were used in Examples 1 and 4 and the other examples, good results were obtained in any of the verifications of both organic acids. In addition, as for the flux containing 2% by mass or more and 15% by mass or less of the organic acid described in paragraph [0016] of the present specification as well, good results were obtained in the esterification suppression verification and the ball misting suppression verification. It is preferable to use an acid.

Examples 2 and 9 contained 10% by mass and 1% by mass of imidazole, and good results were obtained in the esterification suppression verification and the ball-Missing suppression verification. Therefore, it can be said that good results can be obtained by the esterification suppression verification and the ball-missing suppression verification even if the content of imidazole is more than 0% by mass and 10% by mass or less.

Although imidazole was used for the amine of this example, any amine can be used, and for example, a flux containing more than 0% by mass and 10% by mass or less of the amine described in paragraph [0021] of this specification Also, good results were obtained in the esterification suppression verification and the ball missing suppression verification.

The fluxes of Examples 1 to 9 all contain 8% by mass or more and 48% by mass or less of the solvent. Although not shown in the table, even if the content ratio of the solvent in each example is set to more than 0% by mass and 48% by mass or less, good results are obtained in the esterification suppression verification and the ball misting suppression verification. From these results, the content ratio of the solvent is preferably more than 0% by mass and 48% by mass or less, and more preferably 8% by mass or more and 48% by mass or less. Although 1,3-propanediol was used as the solvent in this example, the type of solvent is not limited to this, and even if the solvent described in paragraph [0018] of this specification is used, the esterification suppression verification and the ball are performed. Good results were obtained in the missing suppression verification.

In the present embodiment, the content ratio of each composition is not limited to the ratio described above. Further, any of the surfactant described in paragraph [0023] of the present specification, the halogen compound described in paragraph [0022], the coloring agent such as pigment / pigment / dye, and the antifoaming agent in the above-mentioned example. Also, a flux containing these combinations within the range that does not impair the performance of the present flux has also obtained good results in the esterification suppression verification and the ball-missing suppression verification.

In addition, after confirming the state of the electrode of each board | substrate visually after the ball | bowling suppression suppression verification mentioned above, the electrode of the board | substrate which apply | coated the flux of each Example had few flux residues, and it was not necessary to wash | clean. Moreover, even if the residue remained, it was water washable. Also from this, it can be said that the flux of each example is a flux having good solderability.

In this example, the esterification of the organic acid is suppressed by hydrolyzing the organic acid ester by increasing the water content ratio more than before, but the present invention is not limited thereto. Referring to the concentration formula (4), it is considered that the concentration of the organic acid [R1COOH] can also be increased by increasing the concentration [R1COOR2] of the organic acid ester. Therefore, esterification of the organic acid may be suppressed by forming an organic acid ester in advance and adding it to the flux of the present embodiment. As an organic acid ester to add, the ester compound produced | generated from the organic acid to add and a solvent is preferable.

In the present embodiment, the ball missing suppression verification is performed using solder balls, but the present invention is not limited to this. When the flux obtained good results in the above-mentioned esterification suppression verification and ball-missing suppression verification is used for mounting a metal-cored core ball or metal core column on a substrate, the core ball is also a metal core The column can be stably mounted without moving and solder bumps can be formed at desired positions.

Claims

40% by weight or more and 90% by weight or less of water, 2% by weight or more and 15% by weight or less of organic acid, and 0% by weight or more and 48% by weight or less of a solvent having a hydroxy group,
The content ratio of the carboxylic acid ester unit esterified by the hydroxy group and the organic acid contained in the solvent is 0 unit mol% when the molar mass% of the organic acid carboxyl group unit possessed by the organic acid is 100 unit mol% More than 50 unit mol% or less,
The organic acid is glutaric acid, phenyl succinic acid, succinic acid, malonic acid, adipic acid, azelaic acid, glycolic acid, diglycolic acid, thioglycolic acid, thiodiglycolic acid, propionic acid, 2,2-bishydroxymethyl A flux characterized by containing at least one of propionic acid, 2,2-bishydroxymethylbutanoic acid, malic acid, tartaric acid and trimer acid.
The flux according to claim 1, wherein a content ratio of the water is 40% by mass to 80% by mass.
The flux according to claim 1 or 2, wherein a content ratio of the solvent is 8% by mass or more and 48% by mass or less.
Containing more than 0% by mass and 10% by mass or less of amine
The above-mentioned amine contains at least one selected from imidazoles, aliphatic amines, aromatic amines, amino alcohols, polyoxyalkylene type alkylamines, terminal amine polyoxyalkylenes, and amine hydrohalides. A flux according to any one of the preceding claims.